The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.
This invention relates to preparation of metal nitrides, particularly preparation thereof by methods of reduced toxicity.
The present invention relates to semiconductor materials, and, in particular, relates to nitride materials including GaN.
Gallium nitride was first grown by H. P. Maruska and J. J. Tietjen (Applied Physics Letters, 15 (1969) 32) using hydride vapor phase epitaxy (HVPE). It involves the use of gaseous hydrogen chloride to flow over and pick up the metal and produce the metal chloride. The metal chloride is then reacted with ammonia to form the metal nitride. Substrates of choice for the growth of the metal nitride are sapphire (Al2O3) or silicon carbide (SiC). This process is isolated from the atmosphere by a fused quartz reactor tube and is typically carried out at a temperature of 1050xc2x0 C. Today, this is still one of the methods of choice for growing nitrides.
One drawback to the use of hydrogen chloride is the toxic and corrosive nature of the gas. All components used in the system must be very dry or the parts (i.e. stainless steel valves, mass flow controllers, tubing, fittings, and connections) will oxidize, rendering the system useless. Hydrogen chloride is toxic in that it will form hydrochloric acid upon contact with water in the eyes or lungs or elsewhere.
In other prior art there is U.S. Pat. No. 6,113,985 (2000), which relates to the preparation of metal nitrides but in needles rather then in crystals or film form.
Accordingly there is need and market for a process for producing metal nitrides such as GaN, AlN, InN or ternary or quaternary combinations thereof in a manner that overcomes the above prior art shortcomings.
There has now been discovered a method for producing the above and other metal nitrides in a reduced toxic or nontoxic manner.
Broadly, the present invention provides a method for forming metal nitrides (MN) which includes contacting metal (M) with hydrogen iodide (HI) or iodine (I2) vapor to form the metal iodide (MI) and then contacting the MI with ammonia to form the MN.
Such MN is preferably in the form of gallium nitride (GaN), aluminum nitride (AlN), indium nitride (InN) or quaternary or ternary combinations thereof.
The invention also provides a reactor for forming a metal nitride (MN) comprising,
a) a first container,
b) the container having an upstream inlet, followed by an upstream boat for iodine (I2), a second boat for M spaced downstream from the upstream boat and an outlet located downstream from the second boat,
c) means for heating the two boats,
d) means for flowing iodine from the first boat or for flowing hydrogen iodide (HI) from the inlet), downstream to the second boat, to contact the M to form MI vapor and flowing the MI vapor out the outlet and
e) means to contact the outlet MI vapor with ammonia to form the MN.
Definitions:
By xe2x80x9cammoniaxe2x80x9d as used herein, is meant ammonia gas.
By xe2x80x9cMNxe2x80x9d, as used herein, is meant metal nitride or metal nitrides.
By xe2x80x9cheated metalxe2x80x9d, as used herein, is meant metal heated from 500 to 1000xc2x0 C., including molten metal.
As will be seen herein, the invention provides a two-step process in which the metal iodide (MI) is formed in the first step, which MI is subsequently converted to MN in the second step, all at ambient pressure, which deposits in the forms noted herein. Such process is known as Iodine Vapor Phase Growth (IVPG).